package com.peaksport.framework.uuid;

import java.util.Arrays;
import java.util.Random;

/**
 * Created by jinbin_guo on 2018-04-19.
 */
public class Base64Encoder {
    private static final char intToBase64[] = {
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
            'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
            'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
            'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
            'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
            'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
            '8', '9', '+', '/'
    };
    private static final char intToAltBase64[] = {
            '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',',
            '-', '.', ':', ';', '<', '>', '@', '[', ']', '^',
            '`', '_', '{', '|', '}', '~', 'a', 'b', 'c', 'd',
            'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
            'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
            'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
            '8', '9', '+', '?'
    };
    private static final byte base64ToInt[] = {
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, 62, -1, -1, -1, 63, 52, 53,
            54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
            -1, -1, -1, -1, -1, 0, 1, 2, 3, 4,
            5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
            25, -1, -1, -1, -1, -1, -1, 26, 27, 28,
            29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
            39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
            49, 50, 51
    };
    private static final byte altBase64ToInt[] = {
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, 0, 1, 2, 3, 4, 5, 6,
            7, 8, -1, 62, 9, 10, 11, -1, 52, 53,
            54, 55, 56, 57, 58, 59, 60, 61, 12, 13,
            14, -1, 15, 63, 16, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, 17, -1, 18, 19, 21, 20, 26, 27, 28,
            29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
            39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
            49, 50, 51, 22, 23, 24, 25
    };


    public static String byteArrayToBase64(byte a[]) {
        return byteArrayToBase64(a, false);
    }

    public static String byteArrayToAltBase64(byte a[]) {
        return byteArrayToBase64(a, true);
    }

    private static String byteArrayToBase64(byte a[], boolean alternate) {
        int aLen = a.length;
        int numFullGroups = aLen / 3;
        int numBytesInPartialGroup = aLen - 3 * numFullGroups;
        int resultLen = 4 * ((aLen + 2) / 3);
        StringBuffer result = new StringBuffer(resultLen);
        char intToAlpha[] = alternate ? intToAltBase64 : intToBase64;
        int inCursor = 0;
        for(int i = 0; i < numFullGroups; i++) {
            int byte0 = a[inCursor++] & 255;
            int byte1 = a[inCursor++] & 255;
            int byte2 = a[inCursor++] & 255;
            result.append(intToAlpha[byte0 >> 2]);
            result.append(intToAlpha[byte0 << 4 & 63 | byte1 >> 4]);
            result.append(intToAlpha[byte1 << 2 & 63 | byte2 >> 6]);
            result.append(intToAlpha[byte2 & 63]);
        }

        if(numBytesInPartialGroup != 0) {
            int byte0 = a[inCursor++] & 255;
            result.append(intToAlpha[byte0 >> 2]);
            if(numBytesInPartialGroup == 1) {
                result.append(intToAlpha[byte0 << 4 & 63]);
                result.append("==");
            } else {
                int byte1 = a[inCursor++] & 255;
                result.append(intToAlpha[byte0 << 4 & 63 | byte1 >> 4]);
                result.append(intToAlpha[byte1 << 2 & 63]);
                result.append('=');
            }
        }
        return result.toString();
    }

    public static byte[] base64ToByteArray(String s) {
        return base64ToByteArray(s, false);
    }

    public static byte[] altBase64ToByteArray(String s) {
        return base64ToByteArray(s, true);
    }

    private static byte[] base64ToByteArray(String s, boolean alternate) {
        byte alphaToInt[] = alternate ? altBase64ToInt : base64ToInt;
        int sLen = s.length();
        int numGroups = sLen / 4;
        if(4 * numGroups != sLen)
            throw new IllegalArgumentException("String length must be a multiple of four.");
        int missingBytesInLastGroup = 0;
        int numFullGroups = numGroups;
        if(sLen != 0) {
            if(s.charAt(sLen - 1) == '=') {
                missingBytesInLastGroup++;
                numFullGroups--;
            }
            if(s.charAt(sLen - 2) == '=')
                missingBytesInLastGroup++;
        }
        byte result[] = new byte[3 * numGroups - missingBytesInLastGroup];
        int inCursor = 0;
        int outCursor = 0;
        for(int i = 0; i < numFullGroups; i++) {
            int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
            int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
            int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
            int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);
            result[outCursor++] = (byte)(ch0 << 2 | ch1 >> 4);
            result[outCursor++] = (byte)(ch1 << 4 | ch2 >> 2);
            result[outCursor++] = (byte)(ch2 << 6 | ch3);
        }

        if(missingBytesInLastGroup != 0) {
            int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
            int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
            result[outCursor++] = (byte)(ch0 << 2 | ch1 >> 4);
            if(missingBytesInLastGroup == 1)
            {
                int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
                result[outCursor++] = (byte)(ch1 << 4 | ch2 >> 2);
            }
        }
        return result;
    }

    private static int base64toInt(char c, byte alphaToInt[]) {
        int result = alphaToInt[c];
        if(result < 0)
            throw new IllegalArgumentException((new StringBuilder()).append("Illegal character ").append(c).toString());
        else
            return result;
    }

    public static void main(String args[])  {
        int numRuns = Integer.parseInt(args[0]);
        int numBytes = Integer.parseInt(args[1]);
        Random rnd = new Random();
        for(int i = 0; i < numRuns; i++)  {
            for(int j = 0; j < numBytes; j++)  {
                byte arr[] = new byte[j];
                for(int k = 0; k < j; k++)
                    arr[k] = (byte)rnd.nextInt();

                String s = byteArrayToBase64(arr);
                byte b[] = base64ToByteArray(s);
                if(!Arrays.equals(arr, b))
                    System.out.println("Dismal failure!");
                s = byteArrayToAltBase64(arr);
                b = altBase64ToByteArray(s);
                if(!Arrays.equals(arr, b))
                    System.out.println("Alternate dismal failure!");
            }

        }

    }
}
